Semiconductor light emitting element and method for manufacturing same

ABSTRACT

According to one embodiment, a semiconductor light emitting element includes a conductive substrate, a bonding portion, an intermediate metal film, a first electrode, a semiconductor stacked body and a second electrode. The bonding portion is provided on the support substrate and including a first metal film. The intermediate metal film is provided on the bonding portion and having a larger linear expansion coefficient than the first metal film. The first electrode is provided on the intermediate metal film and includes a second metal film having a larger linear expansion coefficient than the intermediate metal film. The semiconductor stacked body is provided on the first electrode and including a light emitting portion. The second electrode is provided on the semiconductor stacked body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2010-049418, filed on Mar. 5,2010; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor lightemitting element and a method for manufacturing the same.

BACKGROUND

Recently, semiconductor light emitting elements with a sandwichelectrode structure have been drawing attention. In this structure, thelight emitting element is sandwiched between electrodes above and belowthe element. For instance, an LED (light emitting diode) is a typicalexample of such light emitting elements. A manufacturing processtherefor is as follows. On a growth substrate made of sapphire, forinstance, a semiconductor stacked body including a light emittingportion is formed. Next, a conductive substrate is bonded to a majorsurface of the semiconductor stacked body on the opposite side from thegrowth substrate. Then, the growth substrate is removed from thesemiconductor stacked body. An electrode is formed on the surface of thesemiconductor stacked body exposed by the removal of the growthsubstrate. Another electrode is formed on the conductive substrate.

With regard to the aforementioned process, a laser lift-off method hasbeen proposed as a method for removing the growth substrate from thesemiconductor stacked body. However, if the laser lift-off method isused to remove the growth substrate from the semiconductor stacked body,peeling may occur at the interface between the electrode of thesemiconductor stacked body and the bonding portion, the bonding portionbeing interposed between the electrode and the conductive substrate.

In this context, there is demand for improving the reliability andmanufacturing yield of semiconductor light emitting elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view describing an examplestructure of a semiconductor light emitting element according to a firstembodiment;

FIG. 2 is a schematic cross-sectional view describing an examplestructure of a semiconductor light emitting element according to acomparative example;

FIG. 3 is a schematic cross-sectional view describing an exampleconfiguration of the principal part of the semiconductor light emittingelement according to the first embodiment;

FIGS. 4A to 6C are schematic cross-sectional views sequentiallydescribing an example process for manufacturing a semiconductor lightemitting element;

FIG. 7 is a schematic cross-sectional view describing part of a processfor manufacturing the semiconductor light emitting element according tothe comparative example;

FIGS. 8A and 8B are schematic cross-sectional views describing anexample structure of a semiconductor light emitting element according toa third embodiment;

FIGS. 9A to 11D are schematic cross-sectional views sequentiallydescribing an example process for manufacturing a semiconductor lightemitting element; and

FIG. 12 is a schematic cross-sectional view describing an exampleconfiguration of a semiconductor light emitting device according to afifth embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a semiconductor light emittingelement includes a conductive substrate, a bonding portion, anintermediate metal film, a first electrode, a semiconductor stacked bodyand a second electrode. The bonding portion is provided on theconductive substrate and including a first metal film. The intermediatemetal film is provided on the bonding portion and having a larger linearexpansion coefficient than the first metal film. The first electrode isprovided on the intermediate metal film and includes a second metal filmhaving a larger linear expansion coefficient than the intermediate metalfilm. The semiconductor stacked body is provided on the first electrodeand including a light emitting portion. The second electrode is providedon the semiconductor stacked body.

Embodiments of the invention will now be described with reference to thedrawings.

The drawings are schematic or conceptual. The relationship between thethickness and the width of each portion, and the size ratio between theportions, for instance, are not necessarily identical to those inreality. Furthermore, the same portion may be shown with differentdimensions or ratios depending on the figures.

In the specification and the drawings, the same components as thosedescribed previously with reference to earlier figures are labeled withlike reference numerals, and the detailed description thereof is omittedas appropriate.

First Embodiment

FIG. 1 is a schematic cross-sectional view describing an examplestructure of a semiconductor light emitting element according to a firstembodiment.

As shown in FIG. 1, the semiconductor light emitting element 110according to the first embodiment includes a support substrate (aconductive substrate) 70, a bonding portion 40 provided on the supportsubstrate 70, an intermediate metal film 50 provided on the bondingportion 40, a first electrode 30 provided on the intermediate metal film50, a semiconductor stacked body 10 provided on the first electrode 30,and a second electrode 20 provided on the semiconductor stacked body 10.

The support substrate 70 is a substrate of a semiconductor such assilicon (Si) or germanium (Ge). Alternatively, the support substrate 70may be made of a metal such as copper (Cu), molybdenum (Mo), or an alloycontaining such metals.

The bonding portion 40 is a member bonding the semiconductor stackedbody 10 to the support substrate 70. The bonding portion 40 includes afirst bonding layer 41 previously provided on the first electrode 30side, and a second bonding layer 42 previously provided on the supportsubstrate 70 side. The bonding portion 40 is a bonded structure of thefirst bonding layer 41 and the second bonding layer 42. Hence, the firstbonding layer 41 and the second bonding layer 42 may be eitherintegrated together in the bonded state, or partly integrated, at theboundary therebetween.

The first bonding layer 41 is illustratively a metal multilayer filmincluding a bonding metal film 411 (a first metal film in thesemiconductor light emitting element), a bonding metal film 412, and abonding metal film 413 stacked in this order from the first electrode 30side. The bonding metal film 411 is illustratively made of Ti. Thebonding metal film 412 is illustratively made of Pt. The bonding metalfilm 413 is illustratively made of Au.

The second bonding layer 42 is illustratively a metal multilayer filmincluding a bonding metal film 421, a bonding metal film 422, and abonding metal film 423 stacked in this order from the support substrate70 side. The bonding metal film 421 is illustratively made of Ti. Thebonding metal film 422 is illustratively made of Pt. The bonding metalfilm 423 is illustratively made of Au.

The first electrode 30 is provided on a second major surface 10 b of thesemiconductor stacked body 10 on the opposite side from its first majorsurface 10 a. The first electrode 30 is illustratively a p-side mainelectrode of the semiconductor light emitting element 110. The firstelectrode 30 is illustratively a metal multilayer film. The firstelectrode 30 illustrated in FIG. 1 is a metal multilayer film includingan electrode metal film 310 and an electrode metal film 320 (a secondmetal film in the semiconductor light emitting element) stacked in thisorder from the second major surface 10 b of the semiconductor stackedbody 10.

The electrode metal film 310 is illustratively made of Ni. The electrodemetal film 310 provides ohmic contact with the semiconductor stackedbody 10. The electrode metal film 320 is illustratively made of Ag. Theelectrode metal film 320 serves for electrical continuity with theelectrode metal film 310. In addition, the electrode metal film 320 alsofunctions as a reflective film for reflecting light emitted from thelight emitting portion of the semiconductor stacked body 10.

The semiconductor stacked body 10 is illustratively an LED (lightemitting diode). The semiconductor stacked body 10 includes a lightemitting portion provided between the first semiconductor layer and thesecond semiconductor layer. By way of example, the light emittingportion has an MQW (multi-quantum well) structure ofIn_(0.15)Ga_(0.85)N/In_(0.02)Ga_(0.98)N. Blue color or violet color, forinstance, is emitted from the light emitting portion.

The second electrode 20 is provided on at least part of the first majorsurface 10 a of the semiconductor stacked body 10. The second electrode20 is illustratively an n-side main electrode of the semiconductor lightemitting element 110. The second electrode 20 is illustratively made ofconductive film such as ITO (indium tin oxide) or metal film.Alternatively, the second electrode 20 is illustratively made of astacked body of AuGe/Mo/Au stacked in this order, a stacked body ofTi/Pt/Au stacked in this order, or a stacked body of Cr/Ti/Au stacked inthis order from the first major surface 10 a of the semiconductorstacked body 10. In the case of using ITO or a translucent metal filmfor the second electrode 20, light emitted from the semiconductorstacked body 10 can be extracted outside also from the electrode 20side.

In the semiconductor light emitting element 110, an intermediate metalfilm 50 is provided between the electrode metal film 320 of the firstelectrode 30 and the bonding metal film 411 of the bonding portion 40(first bonding layer 41). The linear expansion coefficient of theintermediate metal film 50 is smaller than the linear expansioncoefficient of the electrode metal film 320, and larger than the linearexpansion coefficient of the bonding metal film 411. The intermediatemetal film 50 is illustratively made of Ni.

A protective film 60 is formed so as to cover a part of the first majorsurface 10 a, a side surface of the semiconductor stacked body 10, aside surface of the first electrode 30, a side surface of theintermediate metal film 50, a side surface of the first bonding layer41, and a part of upper surface of the second bonding layer 42.

In the semiconductor light emitting element 110, the intermediate metalfilm 50 as described above enhances adhesion between the first electrode30 and the bonding portion 40 (first bonding layer 41). This suppressespeeling at the interface between the first electrode 30 and the bondingportion 40 when performing laser lift-off.

FIG. 2 is a schematic cross-sectional view describing an examplestructure of a semiconductor light emitting element according to aconventional example.

As shown in FIG. 2, the semiconductor light emitting element 190according to the comparative example includes a support substrate 70, abonding portion 40 provided on the support substrate 70, a firstelectrode 30 provided on the bonding portion 40, a semiconductor stackedbody 10 provided on the first electrode 30, and a second electrode 20provided on the semiconductor stacked body 10.

In the semiconductor light emitting element 190, the electrode metalfilm 320 of the first electrode 30 is directly bonded to the bondingmetal film 411 of the first bonding layer 41 in the bonding portion 40.In contrast, the semiconductor light emitting element 110 includes anintermediate metal film 50 interposed therebetween. In this point, thesemiconductor light emitting element 190 is different from thesemiconductor light emitting element 110.

In the semiconductor light emitting element 190, because the electrodemetal film 320 of the first electrode 30 is directly bonded to thebonding metal film 411 of the bonding portion 40, it is difficult toachieve sufficient bonding strength between the electrode metal film 320and the bonding metal film 411. Hence, peeling may occur at theinterface between the electrode metal film 320 and the bonding metalfilm 411 when the growth substrate is removed by laser lift-off.

In the semiconductor light emitting element 110 according to the firstembodiment, an intermediate metal film 50 is provided between theelectrode metal film 320 and the bonding metal film 411. In thisconfiguration, the linear expansion coefficient difference between theelectrode metal film 320 and the intermediate metal film 50, and thelinear expansion coefficient difference between the intermediate metalfilm 50 and the bonding metal film 411, are smaller than the linearexpansion coefficient difference between the electrode metal film 320and the bonding metal film 411.

Adhesion strength between metal films is higher for a smaller linearexpansion coefficient difference between the metal films. Hence,adhesion strength between metal films from the electrode metal film 320to the bonding metal film 411 is higher in the semiconductor lightemitting element 110 according to this embodiment than in thesemiconductor light emitting element 190 according to the comparativeexample. Thus, separation at the interface between the electrode metalfilm 320 and the bonding metal film 411 is suppressed when the growth isremoved by laser lift-off.

FIG. 3 is a schematic cross-sectional view describing an exampleconfiguration of the principal part of the semiconductor light emittingelement according to the first embodiment.

FIG. 3 primarily illustrates an example configuration of thesemiconductor stacked body 10, the first electrode 30, and the bondingportion 40.

The first electrode 30 is a multilayer metal film including electrodemetal films 310 and 320 stacked in this order from the second majorsurface 10 b of the semiconductor stacked body 10. The bonding portion40 is a bonded structure of the first bonding layer 41 and the secondbonding layer 42. The first bonding layer 41 is a multilayer metal filmincluding bonding metal films 411, 412, and 413 stacked in this orderfrom the first electrode 30 side.

As described earlier, the linear expansion coefficient of theintermediate metal film 50 lies between the linear expansion coefficientof the electrode metal film 320 and the linear expansion coefficient ofthe bonding metal film 411.

Here, the linear expansion coefficient of Ag used for the electrodemetal film 320 is 19.1×10⁻⁶/° C. The linear expansion coefficient of Tiused for the bonding metal film 411 is 8.9×10⁻⁶/° C.

Besides Ni, the intermediate metal film 50 can illustratively be made ofone selected from Pt, Rh, and Pd.

Here, the linear expansion coefficient of Ni is 13.3×10⁻⁶/° C. Thelinear expansion coefficient of Pt is 8.98×10⁻⁶/° C. The linearexpansion coefficient of Rh is 9.6×10⁻⁶/° C. The linear expansioncoefficient of Pd is 10.6×10⁻⁶/° C. Any of these linear expansioncoefficients lies between the linear expansion coefficient of theelectrode metal film 320 and the linear expansion coefficient of thebonding metal film 411. This decreases the linear expansion coefficientdifference of metal films between the first electrode 30 and the firstbonding layer 41, thereby enhancing adhesion strength.

The film thickness d1 of the intermediate metal film 50 may be largerthan the film thickness d2 of the electrode metal film 310 (third metalfilm) of the first electrode 30. For instance, the film thickness d2 ofthe electrode metal film 310 is illustratively 1 nanometer (nm). On theother hand, the film thickness d1 of the intermediate metal film 50 isillustratively 50 nanometers (nm) or more and 150 nm or less. The filmthickness d2 of the electrode metal film 310 is set to a thickness suchas to transmit of light into the electrode metal film 320 used as areflective film. On the other hand, the film thickness d1 of theintermediate metal film 50 is set to a thickness such as to relax stressbetween the electrode metal film 320 and the bonding metal film 411.

In the case of using GaN for the semiconductor stacked body 10, theintermediate metal film 50 serves to suppress diffusion of Ga from thesemiconductor stacked body 10 into the bonding portion 40. Diffusion ofGa into the bonding portion 40 decreases bonding strength in the bondingportion 40. The intermediate metal film 50 suppresses the diffusion ofGa into the bonding portion 40, and hence can prevent the decrease ofadhesion between the first electrode 30 and the bonding portion 40(first bonding layer 41).

In view of sufficiently developing the function of suppressing thediffusion of Ga, it is desirable that the film thickness d1 of theintermediate metal film 50 be thicker than the film thickness d2 of theelectrode metal film 310.

The electrode metal film 310 is illustratively made of the same materialas the intermediate metal film 50. The electrode metal film 310illustrated in FIG. 3 is made of the same material, e.g. Ni, as theintermediate metal film 50.

In the case of using Ag for the electrode metal film 320, theintermediate metal film 50 suppresses penetration of the first bondinglayer 41 by Ag constituting the electrode metal film 320.

This prevents the decrease of bonding strength between the firstelectrode 30 and the first bonding layer 41.

Second Embodiment

An example method for manufacturing a semiconductor light emittingelement according to a second embodiment is described.

FIGS. 4A to 6C are schematic cross-sectional views sequentiallydescribing an example process for manufacturing a semiconductor lightemitting element 110.

In this embodiment, a substrate illustratively made of sapphire is usedas a growth substrate 80 for growing a semiconductor stacked body 10.

First, as shown in FIG. 4A, a semiconductor stacked body 10 is formed onthe growth substrate 80. The thickness of the growth substrate 80 isillustratively 300-500 micrometers (μm). The semiconductor stacked body10 is formed on the growth substrate 80 by epitaxial growth.

Next, a first electrode 30 is formed on the semiconductor stacked body10. The first electrode 30 is illustratively a multilayer metal film ofelectrode metal films 310 and 320 (a first metal film in themanufacturing method). Subsequently, an intermediate metal film 50 isformed on the first electrode 30. Furthermore, a first bonding layer 41is formed on the intermediate metal film 50. The first bonding layer 41is illustratively a multilayer metal film of bonding metal films 411 (asecond metal film in the manufacturing method), 412, and 413. The firstelectrode 30, the intermediate metal film 50, and the first bondinglayer 41 are formed by sputtering or CVD (chemical vapor deposition),for instance.

Next, as shown in FIG. 4B, the semiconductor stacked body 10, the firstelectrode 30, the intermediate metal film 50, and the first bondinglayer 41 are selectively etched and divided on the growth substrate 80.The division is performed for each chip. By way of example, FIG. 4Bshows a divided state corresponding to three chips. The etching processmay be either dry etching or wet etching. Alternatively, the divisionmay be performed by laser processing.

Next, as shown in FIG. 4C, a support substrate 70 with a second bondinglayer 42 provided thereon is prepared. Then, the second bonding layer 42is brought into face-to-face contact with the first bonding layer 41.Thus, the semiconductor stacked body 10, the first electrode 30, theintermediate metal film 50, and the bonding portion 40 (first bondinglayer 41, second bonding layer 42) are sandwiched between the growthsubstrate 80 and the support substrate 70.

Then, heating treatment or ultrasonic treatment is performed to causeinterdiffusion between the first bonding layer 41 and the second bondinglayer 42, thereby bonding them together. More specifically, with thefirst bonding layer 41 and the second bonding layer 42 opposed to eachother, a load of e.g. 5 kgf/cm² or more and 500 kgf/cm² or less isapplied thereto, and they are heated to e.g. 200° C. or more and 400° C.or less. This causes interdiffusion between the first bonding layer 41and the second bonding layer 42, thereby forming a bonding portion 40.Thus, the semiconductor stacked body 10 and the support substrate 70 arebonded. The support substrate 70 also functions as a heat sink, forinstance. Here, the first electrode 30 and the intermediate metal film50 are interposed between the semiconductor stacked body 10 and thebonding portion 40.

Next, as shown in FIG. 5A, laser lift-off (LLO) is performed to removethe growth substrate 80 from the semiconductor stacked body 10. Laserlight 75 is produced using, for instance, an ArF laser (wavelength 193nm), KrF laser (wavelength 248 nm), XeCl laser (wavelength 308 nm), orXeF laser (wavelength 353 nm).

The laser light 75 is transmitted through the growth substrate 80 to thesemiconductor stacked body 10. Here, at the interface between the growthsubstrate 80 and the semiconductor stacked body 10, the semiconductorstacked body 10 absorbs the energy of the laser light 75. Thus, theIII-V nitride components e.g. GaN in the semiconductor stacked body 10is thermally decomposed as shown in the following reaction formula.

GaN→Ga+1/2N₂↑

Consequently, as shown in FIG. 5B, the growth substrate 80 is removedfrom the semiconductor stacked body 10.

FIG. 7 is a schematic cross-sectional view describing part of a processfor manufacturing the semiconductor light emitting element 190 accordingto the comparative example.

FIG. 7 shows an example situation in which the same laser lift-off as inFIG. 5B is performed in the process for manufacturing the semiconductorlight emitting element 190 according to the comparative example.

In the comparative example, the first electrode 30 is directly bonded tothe first bonding layer 41. Because the intermediate metal film 50 usedin this embodiment is not interposed, adhesion strength between thefirst electrode 30 and the first bonding layer 41 may be insufficient.For instance, between the first electrode 30 and the first bonding layer41, stress has been accumulated by thermal history during bonding andlaser lift-off. This stress causes the decrease of adhesion strengthbetween the first electrode 30 and the first bonding layer 41.

If the growth substrate 80 in this state is removed by laser lift-off,peeling may occur between the first electrode 30 and the first bondinglayer 41. This results in decreasing the reliability and manufacturingyield of the semiconductor light emitting element 190.

In contrast, as shown in FIG. 5B, in the manufacturing process accordingto this embodiment, the intermediate metal film 50 is provided betweenthe first electrode 30 and the first bonding layer 41. Hence, there is asufficient adhesion strength between the first electrode 30 and thefirst bonding layer 41. That is, because the intermediate metal film 50is provided between the first electrode 30 and the first bonding layer41, accumulation of stress due to thermal history during bonding andlaser lift-off can be suppressed. Thus, a sufficient adhesion strengthis maintained between the first electrode 30 and the first bonding layer41.

This adhesion strength is sufficiently higher than the adhesion strengthbetween the growth substrate 80 and the semiconductor stacked body 10after irradiation with laser light 75. Hence, when the growth substrate80 is removed by laser lift-off, peeling occurs between the growthsubstrate 80 and the semiconductor stacked body 10, and does not occurbetween the first electrode 30 and the first bonding layer 41.Furthermore, there is no degradation of the surface of the firstelectrode 30.

Next, as shown in FIG. 5C, a protective film 60 is formed so as to coverthe semiconductor stacked body 10, the first electrode 30, theintermediate metal film 50, and the first bonding layer 41. Theprotective film 60 serves to reduce leakage and to protect the element.The protective film 60 is formed by sputtering, for instance. The filmthickness of the protective film 60 is illustratively 100 nm or more and400 nm or less. The protective film 60 is illustratively made ofinsulator.

Next, as shown in FIG. 6A, the protective film 60 is selectivelyremoved. More specifically, the protective film 60 on the first majorsurface 10 a of the semiconductor stacked body 10 is selectively etchedand removed. Then, a second electrode 20 is formed on the first majorsurface 10 a of the semiconductor stacked body 10 exposed by the removalof the protective film 60. The second electrode 20 is illustratively amultilayer metal film of Ti/Pt/Au. The film thickness of Ti isillustratively 20 nm. The film thickness of Pt is illustratively 50 nm.The film thickness of Au is illustratively 700 nm. The second electrode20 is formed by evaporation, for instance.

Subsequently, as shown in FIG. 6B, the support substrate 70 is cut(diced) along a dicing line DL. Thus, as shown in FIG. 6C, asemiconductor light emitting element 110 as a single chip is formed. Insuch a manufacturing method, no peeling occurs between the firstelectrode 30 and the first bonding layer 41 when the growth substrate 80is removed by laser lift-off. Thus, the semiconductor light emittingelement 110 having high reliability can be manufactured with high yield.

Third Embodiment

FIGS. 8A and 8B are schematic cross-sectional views describing anexample structure of a semiconductor light emitting element according toa third embodiment.

FIG. 8A is a schematic cross-sectional view describing the overallstructure of a semiconductor light emitting element 120.

FIG. 8B is a schematic cross-sectional view enlarging the portion A inFIG. 8A.

As shown in FIG. 8A, the semiconductor light emitting element 120according to the third embodiment includes a support substrate (aconductive substrate) 70, a bonding portion 40 provided on the supportsubstrate 70, an intermediate metal film 50 provided on the bondingportion 40, a first electrode 30 provided on the intermediate metal film50, a semiconductor stacked body 10 provided on the first electrode 30,and a second electrode 20 provided on the semiconductor stacked body 10.

A side surface of the semiconductor stacked body 10 is slanted. A firstmajor surface 10 a of the semiconductor stacked body 10 has a smallerarea than a second major surface 10 b of the semiconductor stacked body10.

A protective film 60 is formed so as to cover a part of a first majorsurface 10 a of the semiconductor stacked body 10, a side surface of thesemiconductor stacked body 10, and a part of upper surface of the firstbonding layer 41.

The semiconductor light emitting element 120 according to the thirdembodiment is different from the semiconductor light emitting element110 according to the first embodiment in that the first bonding layer 41in the bonding portion 40 is in contact with at least an end surface 30b of the first electrode 30. The end surface 30 b is also called a sidesurface or an edge surface.

Here, as shown in FIG. 8B, the first bonding layer 41 is a metalmultilayer film of bonding metal films 411, 412, 413, and 414. In thismetal multilayer film, the bonding metal film 414 is resistant toetching for the semiconductor stacked body 10. Furthermore, the bondingmetal film 414 is in contact with at least the end surface 30 b of thefirst electrode 30. The bonding metal film 414 illustrated in FIG. 8B isfurther in contact with the major surface 50 a of the intermediate metalfilm 50, the second major surface 10 b of the semiconductor stacked body10, and the major surface 60 a of the protective film 60.

The bonding metal film 414 is illustratively made of Ni. Because the endsurface 30 b of the first electrode 30 is covered with the bonding metalfilm 414 from the major surface 30 a of the first electrode 30, themetal film of the first electrode 30 is protected during themanufacturing process. The bonding metal film 414 is resistant toetching for the semiconductor stacked body 10. Hence, the bonding metalfilm 414 functions as an etching stopper when the semiconductor stackedbody 10 is etched during the manufacturing process.

With the bonding metal film 414 functioning as an etching stopper,unwanted etching can be suppressed during the etching of thesemiconductor stacked body 10. Unwanted etching causes the etchedportion to fly as dust. If metal is turned to dust, the dust is attachedto the semiconductor light emitting element and causes leakage current.The semiconductor light emitting element 120 according to thisembodiment can suppress the occurrence of leak current.

Fourth Embodiment

An example method for manufacturing a semiconductor light emittingelement according to a fourth embodiment is described.

FIGS. 9A to 11D are schematic cross-sectional views sequentiallydescribing an example process for manufacturing a semiconductor lightemitting element 120.

In this embodiment, a substrate illustratively made of sapphire is usedas a growth substrate 80 for growing a semiconductor stacked body 10.

First, as shown in FIG. 9A, a semiconductor stacked body 10 is formed onthe growth substrate 80. The thickness of the growth substrate 80 isillustratively 300-500 micrometers (μm). The semiconductor stacked body10 is formed on the growth substrate 80 by epitaxial growth.

Next, a first electrode 30 is formed on the semiconductor stacked body10. The first electrode 30 is illustratively a multilayer metal film ofelectrode metal films 310 and 320. Subsequently, an intermediate metalfilm 50 is formed on the first electrode 30. The first electrode 30 andthe intermediate metal film 50 are formed by sputtering or CVD (chemicalvapor deposition), for instance.

Next, as shown in FIG. 9B, the semiconductor stacked body 10, the firstelectrode 30, and the intermediate metal film 50 are selectively etchedand divided on the growth substrate 80. The division is performed foreach chip. By way of example, FIG. 9B shows a divided statecorresponding to three chips. The etching process may be either dryetching or wet etching. Alternatively, the division may be performed bylaser processing.

Next, as shown in FIG. 9C, a first bonding layer 41 is formed so as tocover the divided first electrode 30 and intermediate metal film 50 fromabove. The first bonding layer 41 is illustratively a multilayer metalfilm of bonding metal films 414, 411, 412, and 413. Here, the bondingmetal film 414 is formed in contact with at least the end surface 30 bof the first electrode 30. The bonding metal film 414 illustrated inFIG. 9C is formed on the major surface 50 a and the end surface 50 b ofthe intermediate metal film 50, the end surface 30 b of the firstelectrode 30, and the second major surface 10 b of the semiconductorstacked body 10.

Next, as shown in FIG. 9D, a support substrate 70 with a second bondinglayer 42 provided thereon is prepared. Then, the second bonding layer 42is brought into face-to-face contact with the first bonding layer 41.Thus, the semiconductor stacked body 10, the first electrode 30, theintermediate metal film 50, and the bonding portion 40 (first bondinglayer 41, second bonding layer 42) are sandwiched between the growthsubstrate 80 and the support substrate 70.

Then, heating treatment or ultrasonic treatment is performed to causeinterdiffusion between the first bonding layer and the second bondinglayer 42, thereby bonding them together. More specifically, with thefirst bonding layer 41 and the second bonding layer 42 opposed to eachother, a load of e.g. kgf/cm² or more and 500 kgf/cm² or less is appliedthereto, and they are heated to e.g. 200° C. or more and 400° C. orless. This causes interdiffusion between the first bonding layer 41 andthe second bonding layer 42, thereby forming a bonding portion 40. Thus,the semiconductor stacked body 10 and the support substrate 70 arebonded. The support substrate 70 also functions as a heat sink, forinstance. Here, the first electrode 30 and the intermediate metal film50 are interposed between the semiconductor stacked body 10 and thebonding portion 40.

Next, as shown in FIG. 10A, laser lift-off (LLO) is performed to removethe growth substrate 80 from the semiconductor stacked body 10. Laserlight 75 is produced using, for instance, an ArF laser (wavelength 193nm), KrF laser (wavelength 248 nm), XeCI laser (wavelength 308 nm), orXeF laser (wavelength 353 nm).

The laser light 75 is transmitted through the growth substrate 80 to thesemiconductor stacked body 10. Here, at the interface between the growthsubstrate 80 and the semiconductor stacked body 10, the semiconductorstacked body 10 absorbs the energy of the laser light 75. Thus, theIII-V nitride components e.g. GaN in the semiconductor stacked body 10is thermally decomposed as shown in the following reaction formula.

GaN→Ga+1/2N₂↑

Consequently, as shown in FIG. 10B, the growth substrate 80 is removedfrom the semiconductor stacked body 10.

In the manufacturing process according to this embodiment, theintermediate metal film 50 is provided between the first electrode 30and the first bonding layer 41. Hence, there is a sufficient adhesionstrength between the first electrode 30 and the first bonding layer 41.This adhesion strength is sufficiently higher than the adhesion strengthbetween the growth substrate 80 and the semiconductor stacked body 10after irradiation with laser light 75. Hence, when the growth substrate80 is removed by laser lift-off, peeling occurs between the growthsubstrate 80 and the semiconductor stacked body 10, and does not occurbetween the first electrode 30 and the first bonding layer 41.

Next, as shown in FIG. 10C, a mask material M such as resist is providedon the semiconductor stacked body 10, and the semiconductor stacked body10 is etched at the position between the chips, so as to a side surfaceof the semiconductor stacked body 10 is tapered. The etching isperformed by RIE (reactive ion etching), for instance.

The etching of the semiconductor stacked body 10 proceeds from the firstmajor surface 10 a. When the etching reaches the bonding metal film 414of the first bonding layer 41, the bonding metal film 414 serves as anetching stopper film. The bonding metal film 414 has a sufficientetching selection ratio with respect to the semiconductor stacked body10. Thus, the etching of the semiconductor stacked body 10 stops at theposition of the bonding metal film 414.

Furthermore, the bonding metal film 414 is in contact with the endsurface 30 b of the first electrode 30. Hence, during the etching of thesemiconductor stacked body 10, the end surface 30 b of the firstelectrode 30 is protected by the bonding metal film 414, and can beprevented from being etched. Thus, the manufacturing process accordingto this embodiment suppresses the occurrence of metal dust during theetching of the semiconductor stacked body 10. Hence, the occurrence ofleak current can be suppressed in the completed semiconductor lightemitting element.

Next, as shown in FIG. 11A, a protective film 60 is formed on thesemiconductor stacked body 10. The protective film 60 serves to reduceleakage and to protect the element. The protective film 60 is formed bysputtering, for instance. The film thickness of the protective film 60is illustratively 100 nm or more and 400 nm or less.

Next, as shown in FIG. 11B, the protective film 60 is selectivelyremoved. More specifically, the protective film 60 on the first majorsurface 10 a of the semiconductor stacked body 10 is selectively etchedand removed. Then, a second electrode 20 is formed on the first majorsurface 10 a of the semiconductor stacked body 10 exposed by the removalof the protective film 60. The second electrode 20 is illustratively amultilayer metal film of Ti/Pt/Au. The film thickness of Ti isillustratively 20 nm. The film thickness of Pt is illustratively 50 nm.The film thickness of Au is illustratively 700 nm. The second electrode20 is formed by evaporation, for instance.

Subsequently, as shown in FIG. 11C, the support substrate 70 is cut(diced) along a dicing line DL. Thus, as shown in FIG. 11D, asemiconductor light emitting element 120 as a single chip is formed. Insuch a manufacturing method, peeling is suppressed between the firstelectrode 30 and the first bonding layer 41 when the growth substrate 80is removed by laser lift-off. Furthermore, the occurrence of leakcurrent due to metal dust is suppressed. Thus, the semiconductor lightemitting element 120 having high reliability can be manufactured withhigh yield.

Fifth Embodiment

FIG. 12 is a schematic cross-sectional view describing an exampleconfiguration of a semiconductor light emitting device according to afifth embodiment.

The semiconductor light emitting device 200 includes a semiconductorlight emitting element 110 (120), a molded body 210 enclosing thesemiconductor light emitting element 110 (120), and terminals 220 beingin electrical continuity with the semiconductor light emitting element110 (120) and provided outside the molded body 210.

The chip-shaped semiconductor light emitting element 110 (120) ismounted on a die 215. The semiconductor light emitting element 110 (120)is mounted on the die 215 via a metal film provided on the supportsubstrate 70 side. This brings the first electrode 30 of thesemiconductor light emitting element 110 into electrical continuity withthe die 215.

The die 215 is in electrical continuity with one terminal 220 a. Thesecond electrode 20 of the semiconductor light emitting element 110(120) is connected to the other terminal 220 b via a connecting wire Wsuch as a bonding wire. The terminals 220 (220 a and 220 b) extendoutside from the side surface of the molded body 210, for instance, andare bent from the side surface to the rear surface along the outline ofthe molded body 210.

The semiconductor light emitting device 200 is of the SMD (surface mountdevice) type.

The molded body 210 is a packaging member enclosing the semiconductorlight emitting element 110 (120), the die 215, and part of the terminals220. In the molded body 210, the emission surface side 210 a for lightemission is translucent. If necessary, the emission surface side 210 aof the molded body 210 is provided with phosphor.

The semiconductor light emitting device 200 is mounted on a substrate S.On the rear surface side of the molded body 210, the terminals 220 (220a and 220 b) of the semiconductor light emitting device 200 are bondedwith solder to pads PD provided on the substrate S. Thus, thesemiconductor light emitting device 200 is mechanically fixed onto thesubstrate S, and electrically connected to a circuit (not shown)provided on the substrate S.

Such a semiconductor light emitting device 200 is operable to emit lightwith high reliability because the semiconductor light emitting element110 (120) according to the embodiments is used therein.

It is noted that the semiconductor light emitting device 200 is alsoapplicable to any type other than the SMD type.

The embodiments of the invention have been described. However, theinvention is not limited to these examples.

For instance, in the semiconductor light emitting element 110 (120), theintermediate metal film 50 may be provided as the lowermost layer of thefirst electrode 30. Alternatively, the intermediate metal film 50 may beprovided as the uppermost layer of the bonding portion 40.

Furthermore, for instance, an electronic circuit capable of processinglight signals emitted from the semiconductor light emitting element 110(120) can be integrated on the same support substrate 70 to form anoptoelectronic integrated circuit.

Such an optoelectronic integrated circuit is also encompassed in theembodiments.

Furthermore, the components of the above embodiments can be combinedwith each other as long as technically feasible, and such combinationsare also encompassed within the scope of the invention as long as theyinclude the features of the invention.

Furthermore, those skilled in the art can conceive various modificationsand variations within the spirit of the invention, and it is understoodthat such modifications and variations are also encompassed within thescope of the invention.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

1. A semiconductor light emitting element comprising: a conductivesubstrate; a bonding portion provided on the conductive substrate andincluding a first metal film; an intermediate metal film provided on thebonding portion and having a larger linear expansion coefficient thanthe first metal film; a first electrode provided on the intermediatemetal film and including a second metal film having a larger linearexpansion coefficient than the intermediate metal film; a semiconductorstacked body provided on the first electrode and including a lightemitting portion; and a second electrode provided on the semiconductorstacked body.
 2. The element according to claim 1, wherein the firstelectrode further includes a third metal film provided between thesemiconductor stacked body and the second metal film, and theintermediate metal film has a larger film thickness than the third metalfilm.
 3. The element according to claim 1, wherein the intermediatemetal film is made of one selected from Ni, Pt, Rh, and Pd.
 4. Theelement according to claim 1, wherein the bonding portion is a metalmultilayer film including the first metal film.
 5. The element accordingto claim 1, wherein the first metal film is made of Ni.
 6. The elementaccording to claim 1, wherein the intermediate metal film is providedbetween the first metal film and the second metal film.
 7. The elementaccording to claim 1, wherein the second metal film is made of Ag. 8.The element according to claim 1, wherein the bonding portion includes afourth metal film being in contact with at least an end surface of thefirst electrode and being resistant to etching for the semiconductorstacked body.
 9. The element according to claim 8, wherein the bondingportion is a metal multilayer film including the first metal film.
 10. Amethod for manufacturing a semiconductor light emitting element,comprising: forming a semiconductor stacked body including a lightemitting portion on a growth substrate; forming an electrode including afirst metal film on the semiconductor stacked body; forming anintermediate metal film on the electrode, the intermediate metal filmhaving a smaller linear expansion coefficient than the first metal film;forming a bonding portion on the intermediate metal film, the bondingportion including a second metal film having a smaller linear expansioncoefficient than the intermediate metal film; bonding a supportsubstrate via the bonding portion; and removing the growth substratefrom the semiconductor stacked body by irradiation with laser light froma surface of the growth substrate on opposite side from thesemiconductor stacked body.
 11. The method according to claim 10,wherein the intermediate metal film is made of one selected from Ni, Pt,Rh, and Pd.
 12. The method according to claim 10, wherein the bondingportion is a metal multilayer film including the first metal film. 13.The method according to claim 10, wherein the first metal film is madeof Ni.
 14. The method according to claim 10, wherein the second metalfilm is made of Ag.
 15. A method for manufacturing a semiconductor lightemitting element, comprising: forming a semiconductor stacked bodyincluding a light emitting portion on a growth substrate; forming anelectrode including a first metal film on the semiconductor stackedbody; forming an intermediate metal film on the electrode, theintermediate metal film having a smaller linear expansion coefficientthan the first metal film; selectively etching and dividing theelectrode and the intermediate metal film, and forming a bonding portionso as to cover each of the electrode and the intermediate metal film,the bonding portion including a second metal film having a smallerlinear expansion coefficient than the intermediate metal film; bonding asupport substrate via the bonding portion; removing the growth substratefrom the semiconductor stacked body by irradiation with laser light froma surface of the growth substrate on opposite side from thesemiconductor stacked body; and etching the semiconductor stacked bodyusing the bonding portion as a stopper.
 16. The method according toclaim 15, wherein the intermediate metal film is made of one selectedfrom Ni, Pt, Rh, and Pd.
 17. The method according to claim 15, whereinthe bonding portion is a metal multilayer film including the first metalfilm.
 18. The method according to claim 15, wherein the first metal filmis made of Ni.
 19. The method according to claim 15, wherein the secondmetal film is made of Ag.